Abstract

This study examined the effect of citric acid and ethylenediaminetetraacetic acid (EDTA) application on As, Cr and Cu phytoextraction of maize (Zea mays L.) plant in chromated copper arsenate (CCA) contaminated soil. The soluble and available metal pools in the contaminated soil were determined to be 6.20 ± 0.12 mg/kg and 9.80 ± 0.39 mg/kg As; 34.70 ± 1.10 mg/kg and 69.80 ± 1.44 mg/kg Cr and 18.40 ± 0.70 mg/kg and 46.30 ± 1.16 mg/kg Cu respectively, while the pseudo-total metal contents were 31.70 ± 0.29 mg/kg As, 241.40 ± 1.28 mg/kg Cr and 152.90 ± 1.82 mg/kg Cu. Maize seedlings grown on contaminated soil samples were treated with 100 ml of citric acid and EDTA solutions of various concentrations (0, 2, 4, 6 8 and 10 mM), 15 days after germination. The plants were harvested five days after amendment application and the levels of As, Cr and Cu in the roots and shoots (mg/kg dw) were determined by AAS. Post-harvest mobilization and redistribution of As, Cr and Cu in the soil samples were examined using the BCR sequential extraction method. The total levels of metal uptake (root + shoot) from the unamended soil sample were 6.8 mg/kg As, 5.7 mg/kg Cr and 38.8 mg/kg Cu representing 35, 9 and 37%, respectively, of the potentially available metals. It was found that citric acid and EDTA application markedly enhanced As, Cr and Cu extraction by maize plant, with uptake varying in the order Cu > Cr > As.

Key words: Phytoextraction, citric acid, ethylenediaminetetraacetic acid (EDTA), heavy metals,chromated copper arsenate, maize plant.